Jowl

Twice now my 420SEL has turned into a smoke machine after idling, nose down, on a steep incline. The blue smoke of oil spews out of the tailpipe for about five minutes or so of driving and then disappears. This only happened when the car was running while on a steep nose down incline. I theorize that oil is running backwards, away from the catalytic converter and onto the hot exhaust pipe. I replaced the valve seals not long ago, so it is unlikely to be leaky seals. Other causes?

nomad

Could be worn rings
Normally driving down a slope with the the car in a low gear (lugging) is a good way to check for worn/damaged piston rings